NCCN Guidelines for Patients® | Colon Cancer - page 19

19
NCCN Guidelines for Patients™: Colon Cancer
Version 1.2012
Part 3: Tests of colon cancer
Genetic tests
In the nucleus of a cell, there are coded
instructions for building new cells and
controlling how cells behave. These
instructions are called genes (Figure 10).
Some medical conditions are caused by
abnormal genes passed down from parents
to children.
Genetic conditions that are risk factors for
colon cancer are discussed in Part 2.3. You
may be tested for these genetic conditions
after diagnosis if you haven’t been tested
before. To test for Lynch syndrome, your
doctor may assess for microsatellite
instability. Microsatellite instability is
abnormal changes in deoxyribonucleic acid
(DNA) when DNA is making a copy of itself.
Abnormal genes aren’t always passed down
from parents to children. Instead, there can
be non-inherited changes in genes, some
of which affect colon cancer treatment. The
KRAS
gene is a set of instructions for the
K-Ras protein. If you have metastatic colon
cancer, you should be tested to see if the
KRAS
gene in your tumor is normal. If it is
normal, the
BRAF
gene in your tumor may
be tested next. The
BRAF
gene is a set of
instructions for the B-Raf protein.
Definitions:
Chromosome:
The part
of the cell’s nucleus that
contains deoxyribonucleic
acid
Deoxyribonucleic acid
(DNA):
The part of a cell
containing genes
Imaging:
Medical tests that
take pictures of the inside of
the body
Lymph nodes:
Small
groups of special immune
cells located throughout
the body
Magnetic resonance
imaging (MRI):
A test that
uses powerful magnets to
see body parts
Nucleus:
The control center
of gene activity within a cell
Positron emission
tomography (PET):
A
test that uses radioactive
material to see body parts
Radiologist:
A doctor
who specializes in reading
imaging tests
Figure 10.
Parts of a cell
Illustration Copyright © 2011 Nucleus Medical Media,
All rights reserved.
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